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Publisher Correction to: Characterization of the as-cast microstructure and selected properties of the X-40 Co-based superalloy produced via lost-wax casting

Rakoczy Łukasz, Grudzień-Rakoczy Małgorzata, Cygan Rafał, Rutkowski Bogdan, Kargul Tomasz, Dudziak Tomasz, Rząd Ewa, Milkovič Ondrej, Zielińska-Lipiec Anna

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 4

art. no. e170, 2022

EN

The thermodynamical simulation predicts the phase transformation of M7C3 to M23C6, proven previously via electron microscopy. Some other reported experimental works suggest that this can also take place also during heating [22, 45, 46]. Considering this, the melting process of the primary M7C3 carbide can be that the M7C3 first undergoes a phase transformation into M23C6 and then melts, instead of directly melting. A similar conclusion was given by Gui et al. [47-49] based on experiments on the Co-based superalloy strengthened (in as-cast condition) by M7C3 and MC carbides. It was suggested that the creation of the liquid phase follows the reaction M23C6 + α→L. The reaction was initiated on the M23C6/α interface and proceeded towards the center in the range of 1280 - 1348 ˚C. Before melting, the MC eutectic carbide degenerated, and its morphology changes to a well-rounded shape. Exceeding 1400 ˚C leads to the melting reaction of MC + α→L in the X-40 Co-based superalloy.

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Characterization of the as‑cast microstructure and selected properties of the X‑40 Co‑based superalloy produced via lost‑wax casting

Rakoczy Łukasz, Grudzień-Rakoczy Małgorzata, Cygan Rafał, Rutkowski Bogdan, Kargul Tomasz, Dudziak Tomasz, Rząd Ewa, Milkovič Ondrej, Zielińska-Lipiec Anna

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 3

art. no. e143

EN

The X-40 Co-based superalloy is often used in the aerospace industry directly in as-cast condition and its analysis in this state is essential to understand further possible phase transformations during service. With this in mind, this work focuses on characterizing the material’s as-cast microstructure, phase transformation temperatures and oxidation resistance. Observations and analyses were performed via thermodynamic simulations, X-ray diffraction (XRD), light microscopy (LM), scanning electron microscopy (SEM), scanning-transmission electron microscopy (STEM-HAADF), energy-dispersive X-ray spectroscopy (EDX), dilatometry (DIL) and differential scanning calorimetry (DSC). The microstructure of the dendritic regions consisted of the α matrix, with MC, M7C3 and M23C6 carbides being present in the interdendritic spaces. Based on DIL, it was found that precipitation of the Cr-rich carbides from the saturated α matrix may occur in the range 650-750 °C. DSC determined the incipient melting and liquidus temperatures of the X-40 superalloy during heating to be 1405 °C and 1421 °C, respectively. Based on oxidation resistance tests carried out at 860 °C, it was found that the mass gain after 500 h exposure was 3 times higher in the air than in steam.

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Microstructure and abrasive wear properties of M(Cr,Fe)7C3carbides reinforced high-chromium carbon coating produced by gas tungsten arc welding (GTAW) process

Buytoz Soner, Yildirim M. Mustafa

Archives of Foundry Engineering

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2010

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Vol. 10, iss. 1 spec.

279--286

EN

In the present study, high-chromium ferrochromium carbon hypereutectic alloy powder was coated on AISI 4340 steel by the gas tungsten arc welding (GTAW) process. The coating layers were analyzed by optical microscopy, X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), X-ray energy-dispersive spectroscopy (EDS). Depending on the gas tungsten arc welding pa-rameters, either hypoeutectic or hypereutectic microstructures were produced. Wear tests of the coatings were carried out on a pin-on-disc apparatus as function of contact load. Wear rates of the all coating layers were decreased as a function of the loading. The improvement of abrasive wear resistance of the coating layer could be attributed to the high hardness of the hypereutectic M7C3 carbides in the microstruc-ture. As a result, the microstructure of surface layers, hardness and abrasive wear behaviours showed different characteristics due to the gas tungsten arc welding parameters.

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Compositional changes in carbide M7C3 upon annealing

Palcut M., Vach M., Cicka R., Janovec J.

Archives of Metallurgy and Materials

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2008

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Vol. 53, iss. 4

1157-1164

EN

A lot of work was done on the structure of M7C3 in the past. It was found that this carbide contains an extremely high amount of defects and its structure can be interpreted either as a orthorormbic, hexagonal or trigonal crystal structure. Compositional studies, however, have not been done in detail yet. It has been, therefore, our intention to shed further light into the compositional evolution of carbide M7C3 upon annealing. Four Iow alloy steels 0.9Cr, 0.9Cr-0.25V, 2.5Cr-0.25V-0.4Mo, 0.9Cr-0.25V-0.4Mo (compositions given in mass percents) were annealed for 1000 - 5000 h at temperatures 773 - 993 K in evacuated capsules. Secondary phase particles extracted into carbon replicas were identified by the electron difFraction, and their compositions were determined by the energy dispersive x-ray spectroscopy. In parallel, changes in the Fe/Cr ratio for M7C3 were predicted using the thermodynamic-database program Thermo-Calc and plotted versus the bulk content of carbon, vanadium and chromium. It was shown that the Fe/Cr ratio increases with increasing bulk carbon content for all investigated steels and temperatures considered. On the other hand, it was predicted that the Fe/Cr ratio decreases with increasing bulk vanadium and chromium contents and increasing temperaturę. Molybdenum was found to stabilize the MC carbide, to reduce the molar fraction of M7C3 carbide and to decrease the values of Fe/Cr ratio in M7C3 at lower temperatures. The predictions were found to be in a good agreement with experimental observations, mainly for higher annealing temperatures. The only disagreement was found for the 2.5Cr-0.25V-0.4Mo steel.

PL

Tematyce struktury M7C3 poświęcono w przeszłości wiele prac. Stwierdzono, że węglik ten zawiera ekstremalnie dużą ilość defektów, a jego struktura może być interpretowana zarówno jako ortorombowa, heksagonalna lub trygonalna. Jednakże nie przeprowadzono dotychczas badań składu tej fazy. Tak więc, naszą intencją było rzucenie nowego światła na zmiany składu węglika M7C3 w trakcie wyżarzania. Cztery gatunki stali niskostopowych 0.9Cr, 0.9Cr-0.25V, 2.5Cr-0.25V-0.4Mo, 0.9Cr-0.25V-0.4Mo (składy podano w % wagowych) poddano wyżarzaniu w próżniowych kapsułach przez 1000 - 5000 godzin w temperaturach 773 - 993 K. Cząstki węglików ekstrahowano do repliki węglowej i identyfikowano za pomocą dyfrakcji elektronowej, a ich skład określono metodą spektroskopii dyspersji energii promieniowania rentgenowskiego (EDX). Równolegle, korzystając z termodynamicznej bazy danych programu Thermo-Calc, obliczono prognozowane zmiany parametru Fe/Cr dla M7C3 i przedstawiono je graficznie jako zależności od całkowitej zawartości węgla, wanadu i chromu w stali. Pokazano, że parametr Fe/Cr wzrasta wraz ze wzrostem całkowitej zawartości węgla dla wszystkich zbadanych gatunków stali w rozpatrywanym zakresie temperatur. Z drugiej strony pokazano również, że następuje spadek wartości parametru Fe/Cr ze wzrostem całkowitej zawartości wanadu i chromu oraz obniżaniem temperatury wyżarzania. Stwierdzono, że molibden stabilizuje węglik MC, obniża udział molowy węglika M7C3, a dla najniższych temperatur obniża wartość współczynnika Fe/Cr. Obliczenia prognozujące, zwłaszcza dla wyższych temperatur wyżarzania, okazały się być w dobrej zgodności z obserwacjami eksperymentalnymi. Jedyną rozbieżność zaobserwowano dla stali 2.5Cr-0.25V-0.4Mo.